From my experience those with absolutely ZERO jetting experience ( most of the people I ride with, and up until lately myself included ) have, at one time or another, had problems with spooge, oil build-up and rich running bikes that were jetted rich from the begining. Most people see this as the premix ratio that causes the spooge, fouled plugs, and gooey mess on the exhaust valves. Instead of questioning the jetting one ass-umes that there is too much oil because that is what is seen all over the bike.
By lowering the oil content of the premix the bike will have an easier time burning the gas which equates into fouling fewer plugs, making more power (have you ever tried to light oil on fire? It takes awhile, but gas...BABOOM!) and not having so much oily byproduct making a mess all over the bike. :confused:
Of course we all upin' Idahoe know this is true which is why all the CR500 equiped pipe-movers run 50:1, 60:1, and even 80:1 with 85 octane pump gas and Homelite, or any other generic brand 2 stroke weed wacker oil package in a black quart-sized bottle.
I consider myself lucky. A tiny voice in my head warned me to ignore the advice of those around. I did, and chose Amsoil at 40:1. Not bad, but now I have the power of knowledge on my side. This spring I'll be spending some quality time with my bike, a box full of jets, and some 32:1 to 24:1 with those first numbers hopefully being race gas (if I can find some locally).